Extendable and retractable lead having a snap-fit terminal connector

ABSTRACT

A lead having an extendable and retractable fixation mechanism has a rotating terminal pin at the terminal end which rotates the fixation mechanism at the distal end. As the terminal pin is rotated, the fixation mechanism is extended or retracted from the distal end of the lead. A threaded collar allows for the fixation mechanism to smoothly extend and retract from the lead, and allows for a 1:1 turn ratio between the terminal pin and the fixation mechanism. A fluoroscopic ring disposed at the distal end of the lead provides information during the implantation process.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This patent application is a continuation of U.S. patent applicationSer. No. 10/264,494, filed on Oct. 4, 2002, which is a division of U.S.patent application Ser. No. 09/359,580, filed on Jul. 22, 1999, which isa continuation-in-part of U.S. patent application Ser. No. 09/121,005,filed on Jul. 22, 1998, now U.S. Pat. No. 6,141,594, U.S. patentapplication Ser. No. 09/120,824, filed on Jul. 22, 1998, now issued asU.S. Pat. No. 6,212,434, and U.S. patent application Ser. No.09/184,226, filed on Nov. 2, 1998, now abandoned, each of which isassigned to a common assignee and the specifications of which areincorporated herein by reference in their entirety.

Additionally, this patent application is related to U.S. patentapplication Ser. No. 09/472,098, filed on Dec. 23, 1999 and U.S. patentapplication Ser. No. 10/210,192, filed on Jul. 31, 2002, each of whichis assigned to a common assignee, and the specifications of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to implantable leads. Moreparticularly, it pertains to leads having an extendable and retractablefixation mechanism.

BACKGROUND OF THE INVENTION

Electrodes have been used to stimulate contraction of the heart or toreverse certain life threatening arrhythmias, where electrical energy isapplied to the heart via the electrodes to return the heart to normalrhythm. Electrodes have also been used to sense and deliver pacingpulses to the atrium and ventricle. Cardiac pacing may be performed by atransvenous method or by electrodes implanted directly onto theepicardium. For transvenous pacing systems, a lead having an electrodeis positioned in the right ventricle and/or in the right atrium througha subclavian vein, and the proximal electrode terminals are attached toa pacemaker which is implanted subcutaneously.

Some lead designs have “floating” electrodes or electrodes which are notattached to the endocardial wall of the heart. The floating electrodeslay in the blood pool or against the endocardial wall of the heart andthe electrode may move slightly within the heart. Since the location offloating electrodes is not fixed with respect to the endocardial wall,the electrical performance of these electrodes varies and is generallyless than optimal. Both the electrical sensing capability as well as thepacing delivery capability of such electrodes are suboptimal. The pacingparameters of such a floating electrode are also suboptimal. Inaddition, the floating electrodes can require increased voltage whichunnecessarily drains the battery.

As an alternative to floating electrodes, leads have been provided withpassive fixation elements that affix the electrode to the endocardialwall over time. With passive fixation elements, it can be difficult todetermine whether the lead will affix in the location at which it isimplanted.

Active fixation elements, such as a helix, have also been provided withdistal ends of leads which allow a lead to be affixed to the endocardialwall. The helix is rotated to screw the lead into the endocardial wall.To rotate the helix toward and into the endocardial wall, a stylet isdisposed within the lead and rotated. As the stylet is rotated however,the active fixation element may jump out of the end of the lead anddamage tissue, and/or the helix. In addition, it is difficult for theimplanter to determine how many turns to the stylet is necessary toadvance the helix a certain distance.

A cardiac pacing system typically includes a pulse generator whichsupplies the electrical energy to the lead. The pulse generator may beimplanted into a subcutaneous pocket made in the wall of the chest. Alead coupled with the pulse generator is routed subcutaneously from thepocket to the shoulder or neck where the lead enters a major vein, suchas the subclavian vein, and into the heart. The proximal end of the leadis coupled both electrically and mechanically with the pulse generatorat A distal end of the lead is placed within the heart, and a proximalend is placed within a pacemaker.

When leads with multiple conductors are involved, the conductors areindividually and electrically coupled with the pulse generator at aproximal end of the multiple conductors. The multiple conductors at theproximal end are electrically insulated from each other to preventshorts and limit electrical leakage between conductors. Medical adhesiveis used to insulate the multiple conductors at the proximal end of thelead. However, the process of using medical adhesive is timely andcostly to assemble. In addition, the medical adhesive bondsinconsistently, sometimes resulting in mechanical and electricalseparation between the components.

The proximal end of the lead includes a terminal connection whichprovides the electrical and mechanical connection between the pacemakerand the proximal end of the lead. When inserted into the pacemaker, thecomponents of the terminal connection undergoes axial stress as theimplanter forces the proximal end of the lead into the pacemaker. Afterinserted, the implanter may pull on the lead to ensure the terminal endis sufficiently seated in the pacemaker, placing additional axial stresson the terminal connection.

Accordingly, there is a need for a lead with multiple conductors whichare reliably insulated from one another. What is further needed is alead having a terminal connection which can accommodate axial stressplaced thereon.

SUMMARY OF THE INVENTION

An extendable and retractable lead includes a lead body which extendsfrom a distal end to a proximal end. A conductor is disposed within thelead body and extends from the distal end to the proximal end of thelead body. In addition, the lead includes an electrode base coupled withthe conductor proximate to the distal end of the lead body. Theelectrode base is threadingly coupled with an outer threaded shell. Theelectrode base includes external threads disposed thereon. The lead alsoincludes an active fixation element coupled with the electrode base andthe outer threaded shell.

In one embodiment, the lead includes a movement assembly which isconfigured to extend and retract the active fixation mechanism. Themovement assembly includes a housing having an internally threadedportion and an externally threaded collar which is engaged with theinternally threaded portion. In another embodiment, the movementassembly further includes an internally threaded insert disposed withinthe lead, where the threaded collar is engaged with the threaded insert.

In yet another embodiment, the outer threaded shell is formed ofpolyetheretherketone. Alternatively, the lead further includes a secondouter shell coupled with the outer threaded shell, where the secondouter shell forms a stop for the electrode base. In one embodiment, thesecond outer shell is formed of polyetheretherketone. The outer threadedshell is coupled with the second outer shell, for example, with epoxy.The epoxy comprises, in one embodiment, a mixture of one part EPOTEK353ND to 1.75 parts EPOTEK 353ND-T. In yet another embodiment, the leadfurther includes a fluoroscopic ring disposed about the fixation helix.

A lead includes a lead body extending from a distal end to a proximalend. At least one conductor is disposed within the lead body and extendsfrom the distal end to the proximal end of the lead body. An outerterminal ring is coupled with the lead body, and a sleeve is coupledwith the outer terminal ring, and is also coupled with a terminal pin.The coupling allows for rotational movement between the outer terminalring and the terminal pin. The sleeve is coupled with the outer terminalring or the terminal pin with a snap-fit coupling. The snap-fitcoupling, in one embodiment, comprises a first and second set ofcantilevered hooks. In another embodiment, the snap-fit couplingcomprises an annular flange received in a recess.

In another embodiment, a lead is provided which includes a lead bodyextending from a distal end to a proximal end. At least one conductor isdisposed within the lead body and extends from the distal end to theproximal end of the lead body. An outer terminal ring is coupled withthe lead body, and a sleeve is coupled with the outer terminal ring, andis also coupled with a terminal pin. The sleeve is coupled with theterminal pin with a snap-fit connection.

In yet another embodiment, a lead is provided which includes a lead bodyextending from a distal end to a proximal end. At least one conductor isdisposed within the lead body and extends from the distal end to theproximal end of the lead body. An outer terminal ring is coupled withthe lead body, and a sleeve is coupled with the outer terminal ring, andis also coupled with a terminal pin. The sleeve is coupled with theouter terminal ring or the terminal pin with a press-fit coupling.

A lead includes, in another embodiment, a lead body which is coupledwith an outer terminal ring. The outer terminal ring is coupled with aterminal pin with a snap-fit connection. An insulator is disposedbetween the outer terminal ring and the terminal pin, and in oneembodiment comprises a non-conductive coating. In one embodiment, theouter terminal ring is rotatably coupled with the terminal pin.

In yet another embodiment, a system includes an electronics system whichhas a pulse generator. The pulse generator is electrically coupled witha lead which includes a lead body extending from a distal end to aproximal end. At least one conductor is disposed within the lead bodyand extends from the distal end to the proximal end of the lead body. Anouter terminal ring is coupled with the lead body, and a sleeve iscoupled with the outer terminal ring, and is also coupled with aterminal pin. The coupling allows for rotational movement between theouter terminal ring and the terminal pin. The sleeve is coupled with theouter terminal ring or the terminal pin with a snap-fit coupling. Thesnap-fit coupling, in one embodiment, comprises a first and second setof cantilevered hooks. In another embodiment, the snap-fit couplingcomprises an annular flange received in a recess. In yet anotherembodiment, the lead further includes a movement assembly which isconfigured to extend and retract an active fixation mechanism. Themovement assembly includes a housing having an internally threadedportion and an externally threaded collar which is engaged with theinternally threaded portion. In another embodiment, the movementassembly further includes an internally threaded insert disposed withinthe lead, where the threaded collar is engaged with the threaded insert.

The lead assembly described above provides several advantages, forexample, ease of manufacturability is increased and through put timesare reduced. The individual components can be snapped together, asopposed to waiting for messy bonding or long cure times. Bonding blocks,used for the bonding process, are eliminated, which are expensive,difficult and costly to clean. A consistent and increased strength ofcoupling is achieved using the snap fit design since bonding is variablebased on the operator. Yet another advantage is that the geometry of thesnap fit connector provides an insulation with a known thickness, whichallows for a repeatable dielectric strength.

These and other embodiments, aspects, advantages, and features of thepresent invention will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the art byreference to the following description of the invention and referenceddrawings or by practice of the invention. The aspects, advantages, andfeatures of the invention are realized and attained by means of theinstrumentalities, procedures, and combinations particularly pointed outin the appended claims and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a system for delivering and/orreceiving signals to and from the heart constructed in accordance withone embodiment.

FIG. 2 is a cross-section illustrating a terminal end of a leadconstructed in accordance with one embodiment.

FIG. 3 is a cross-section illustrating a distal end of a leadconstructed in accordance with one embodiment.

FIG. 4 is a cross-section illustrating a distal end of a leadconstructed in accordance with another embodiment.

FIG. 5 is a cross-section illustrating a distal end of a leadconstructed in accordance with another embodiment.

FIG. 6 is a perspective view illustrating a portion of a movementassembly end of a lead constructed in accordance with anotherembodiment.

FIG. 7A is a block diagram of a system with a lead for use with a heartand constructed in accordance with one embodiment.

FIG. 7B is an elevational view of an example of a lead for use in thesystem shown in FIG. 7A.

FIG. 7C is a cross-sectional view of a lead coupled with a pulsegenerator constructed in accordance with one embodiment.

FIG. 8 is an exploded perspective view of an assembly constructed inaccordance with one embodiment.

FIG. 9A is an unexploded cross-sectional view of the assembly shown inFIG. 8 constructed in accordance with one embodiment.

FIG. 9B is a cross-section view of a portion of a lead constructed inaccordance with another embodiment.

FIG. 10 is an exploded perspective view of an assembly constructed inaccordance with another embodiment.

FIG. 11 is an unexploded cross-sectional view of the assembly shown inFIG. 10 constructed in accordance with one embodiment.

FIG. 12 is an exploded perspective view of an assembly constructed inaccordance with yet another embodiment.

FIG. 13 is an unexploded cross-sectional view of the assembly shown inFIG. 13 constructed in accordance with one embodiment.

FIG. 14 is an exploded perspective view of an assembly constructed inaccordance with one embodiment.

FIG. 15 is an unexploded cross-sectional view of the assembly shown inFIG. 14 constructed in accordance with one embodiment.

FIG. 16 is an exploded cross-sectional view of an assembly constructedin accordance with one embodiment.

FIG. 17 is a cross-sectional view of an assembly constructed inaccordance with one embodiment.

FIG. 18 is a cross-sectional view of an assembly constructed inaccordance with another embodiment.

FIG. 19 is an unexploded cross-sectional view of an assembly constructedin accordance with one embodiment.

DESCRIPTION OF THE EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that structuralchanges may be made without departing from the scope of the presentinvention. Therefore, the following detailed description is not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents.

An extendable and retractable lead 110 and lead system 100 areillustrated in FIG. 1. FIG. 1 is a block diagram of a system 100 fordelivering and/or receiving electrical pulses or signals to stimulateand/or sense the heart 102. The system 100 includes a pulse generator105 and a lead 110. The pulse generator 105 includes a source of poweras well as an electronic circuitry portion. The pulse generator 105 is abattery-powered device which generates a series of timed electricaldischarges or pulses. The pulse generator 105 is generally implantedinto a subcutaneous pocket made in the wall of the chest. Alternatively,the pulse generator 105 is placed in a subcutaneous pocket made in theabdomen, or in other locations.

The lead 110 includes a lead body 113 which extends from a proximal end112, where it is coupled with the pulse generator 105, as furtherdiscussed below. The lead 110 extends to a distal end 114, which iscoupled with a portion of a heart 102, when implanted. The distal end114 of the lead 110 includes at least one electrode 116 (FIG. 2) whichelectrically couples the lead 110 with the heart 102. At least oneelectrical conductor 118 (FIG. 2) is disposed within the lead 110 andextends from the proximal end 112 to the distal end 114 of the lead 110.The at least one electrical conductor 118 electrically couples theelectrode 116 with the proximal end 112 of the lead 110. The electricalconductors carry electrical current and pulses between the pulsegenerator 105 and the electrode 116.

FIGS. 2 and 3 illustrate one embodiment of the distal end 114 of thelead 110 in greater detail, where FIG. 2 illustrates the lead 110 in aretracted position and FIG. 3 illustrates the lead 110 in an extendedposition. The electrode 116 comprises a fixation helix 120 which allowsfor the distal end 114 of the lead 110 to be affixed to the heart 102(FIG. 1). The fixation helix 120 is mechanically and electricallycoupled with an electrode base 122. The electrode base 122 ismechanically coupled with the at least one electrical conductor 118,such that as the conductor 118 is rotated, the electrode base 122translates along an axis 113 of the lead 110, as will be furtherdiscussed below. In one embodiment, the electrode base 122 iselectrically coupled with the at least one electrical conductor 118, andthe electrode base 122 is formed of an electrically conductive material,such as metal. Disposed about the electrode base 122 are externalthreads 124, which allow the electrode base 122 to rotate and translatethe fixation helix 120. The electrode base 122 is coupled with an outerthreaded shell 140. In one embodiment, a steroid collar 151 is disposedwithin the distal end 114 of the lead 110.

The threaded shell 140 has internal threads 142 therein. The internalthreads 142 provide a path for the external threads 124 of the electrodebase 122. As the electrode base 122 is rotated, the external threads 124engage with the internal threads 142 and translate the electrode base122 along the axis 113 of the lead 110. In one embodiment, the lead 110includes a stop to prevent the fixation helix 120 from over-extension.The stop comprises, in one embodiment, a stop 144 on the internalthreads 142 which blocks the rotation of the external threads 124. Oncethe external threads 124 reach the stop 144, the electrode base 122 canno longer be rotated and translated out of the lead 110, which preventsthe fixation helix 120 from being overextended into tissue of, forexample, a heart. In another embodiment, the stop comprises a stop 146formed on an outer shell 145 which is disposed adjacent to the electrodecollar 130 (discussed below).

The outer threaded shell 140 and/or the outer shell 145, in oneembodiment, is formed of polyetheretherketone (PEEK). In anotherembodiment, the outer threaded shell 140 is formed of PEEK 150G, lowmelt viscosity. For the PEEK 150G, the melt viscosity ranges from about0.12-0.18 KNs/m², and the tensile strength is greater than or equal to90 MPa. The threaded shell 140, in another embodiment, comprises PEEK450G, standard melt viscosity. For the PEEK 450G, the melt viscosityranges from about 0.38-0.50 KNs/m², and the tensile strength is greaterthan or equal to 90 MPa. The PEEK allows for the outer threaded shell140 to be molded, extruded, or machined for tighter tolerances orproviding precision structures. PEEK is a tough rigid thermoplasticmaterial which is biocompatible.

Proximate to the distal end 114 of the lead 110 is a fluoroscopy ring150, which is disposed about the fixation helix 120. The electrode base122 has, in one embodiment, an electrode collar 130 coupled therewith,such that as the electrode base 122 is translated, the electrode collar130 translates along the axis 113. As the fixation helix 120 is extendedout from the lead 110, the electrode collar 130 translates toward thefluoroscopy ring 150 until the electrode collar 130 abuts a portion thefluoroscopy ring 150, at which point the fixation helix 120 is fullyextended. The collar 130 and the ring 150 allows the implanter to view,under fluoroscopy, when the fixation helix 120 is fully extended.

As discussed above, the outer shell 145, provides a stop for thetranslation of the electrode collar 130. The outer shell 145 is coupledwith the outer threaded shell 140. Epoxy 190, in one embodiment, isdisposed between the outer threaded shell 140 and the outer shell 145.In one embodiment, the epoxy 190 comprises a blend of two differentepoxies. The two different epoxies are EPOTEK® 353ND and EPOTEK® 353ND-Tmade by Epoxy Technology. The two epoxies are mixed in the ratio of 1part EPOTEK® 353ND to 1.75 parts EPOTEK® 353ND-T. The epoxy is cured ata temperature of 150° C. for one hour.

FIGS. 4 and 5 illustrate another embodiment of a lead 200. The lead 200includes a retractable active fixation element 270, which assists inavoiding injury to the patient during implantation. Alternatively, theactive fixation element 270 rotates without translating along the lead200. The lead 200 further includes a movement assembly 202 disposed at adistal end 214 of the lead 200, where the movement assembly 202 isadapted to transport the active fixation element 270 in and out of thelead 200 as the active fixation element 270 is rotated.

Referring again to FIG. 4, the movement assembly 202 includes externalthreads 220 associated therewith. In one embodiment, the externalthreads 220 are disposed about a collar 222 of the lead 200. Theexternal threads 220 are adapted to engage with internal threads 226disposed within a housing 224 of the lead 200. The internal threads 226provide a helical path for the external threads 220. The movementassembly 202 is not, however, limited to the components describedherein. For instance, the external threads 220 and the internal threads226 can be provided on alternative components, and still be consideredwithin the scope of the invention. In one embodiment, an insert 230 isprovided for the internal threads 226, as shown in FIG. 5. As shown inFIG. 5, the insert 230 comprises a semi-cylindrical collar 233, wherethe collar 233 is disposed within the lead 200. In another embodiment, atwo-piece insert is provided which includes a first half and a secondhalf. The first half and the second half are coupled together to form acylindrical collar in which there are internal threads. In oneembodiment, the first half and the second half are molded from plasticmaterial. In another embodiment, the first half and the second half aremachined from, for example, hard plastic materials or metal, or thematerials discussed above.

The insert 230 contains internal threads 226 which are adapted to engagewith the external threads 220 of the collar 222. During use, a terminalpin (FIG. 6) is rotated which causes the collar 222 to rotate. As thecollar 222 is rotated and the external threads 220 and the internalsthreads 226 engage, the active fixation element 270 moves along the axis214 of the lead 200. The movement assembly 202 can be used with a widevariety of leads implementing active fixation, including, but notlimited to, single pass dual chamber pacing leads, single pass dualchamber pacing/defibrillator leads, single chamber pacing leads, andsingle chamber pacing/defibrillator leads.

In another embodiment, a mesh screen 240 is provided at a distal end 214of the lead 200. The mesh screen 240 allows for better tissue in-growth,as well as enhanced sensing capabilities. The mesh screen 240 isdisposed proximate to the active fixation element 270. In oneembodiment, as the active fixation element 270 is translated andextended from the lead 200, mesh screen 240 moves with the activefixation element 270. The fixation element 270 engages the heart tissueand draws the mesh screen 240 into contact with the surface of theheart. In yet another embodiment, a steroid 242 is disposed within thedistal end 214 of the lead 200.

FIG. 6 illustrates one embodiment of the proximal end 112 of a lead 300in greater detail. The lead 300, in one embodiment, incorporates theembodiments discussed for the distal end discussed above and below. Inaddition, the proximal end 112 of lead 300 includes a terminal pin 310which provides the electrical connection between the pulse generator 105(FIG. 1) and the lead 300. The terminal pin 310 is mechanically coupledwith a conductor coil 312. As the terminal pin 310 is rotated, theconductor coil 312 rotates, thereby rotating the electrode base (FIGS. 2and 3) as discussed above.

The lead 300 further includes an outer terminal ring 314 which iscoupled with a lead body 316. An insulator sleeve 318 is disposed overat least a portion of the terminal pin 310, and the insulator sleeve 318insulates the terminal pin 310 from the outer terminal ring 314. In oneembodiment, the sleeve 318 is rotatably coupled with the outer terminalring 314.

The sleeve 318, in another embodiment, is coupled with the terminal pin310 with a snap-fit connection. Alternatively, the sleeve 318 is coupledwith the terminal pin 310 and/or the outer terminal ring 314 with asnap-fit connection. In one embodiment, the sleeve 318 includes at leastone projection 320. The at least one projection 320 is engaged with arecess 330 of the terminal pin 310, and prevents the terminal pin 310from moving axially. The projection 320, in one embodiment, comprises anannular projection disposed about the circumference of the sleeve 318,which allows the terminal pin 310 to rotate relative to the outerterminal ring 314. The annular projection engages within an annularrecess disposed within the circumference of the terminal pin 310. In yetanother embodiment, the sleeve 318 further includes at least one recess322 disposed adjacent to the projection 320. The at least one recess 322receives therein a projection 324 of the terminal pin 310. Theadditional mating male and female components provide increased axialstrength to the connection between the lead 300 and the pulse generator(FIG. 1). In yet another embodiment, the sleeve 318 further includes astop 360 for the outer terminal ring 314.

The sleeve 318 is formed of non-conductive material. In one embodiment,the sleeve 318 is formed of polyetheretherketone (PEEK). In anotherembodiment, the sleeve 318 is formed of PEEK 150G, low melt viscosity.For the PEEK 150G, the melt viscosity ranges from about 0.12-0.18KNs/m², and the tensile strength is greater than or equal to 90 MPa. Thesleeve 318, in another embodiment, comprises PEEK 450G, standard meltviscosity. For the PEEK 450G, the melt viscosity ranges from about0.38-0.50 KNs/m², and the tensile strength is greater than or equal to90 MPa. The PEEK allows for the sleeve 318 to be molded, extruded, ormachined for tighter tolerances or providing precision structures. PEEKis a tough rigid thermoplastic material which is biocompatible.

FIGS. 7A-19 illustrate additional embodiments of the lead and leadsystem. FIG. 7A is a block diagram of a system 1100 for deliveringand/or receiving electrical pulses or signals to stimulate and/or sensethe heart. The system for delivering pulses 1100 includes a pulsegenerator 1105 and a lead 1110. The pulse generator 1105 includes asource of power as well as an electronic circuitry portion. The pulsegenerator 1105 is a battery-powered device which generates a series oftimed electrical discharges or pulses used to initiate depolarization ofexcitable cardiac tissue. The pulse generator 1105 is generallyimplanted into a subcutaneous pocket made in the wall of the chest.Alternatively, the pulse generator 1105 is placed in a subcutaneouspocket made in the abdomen, or in other locations. An enlargement of theconnection between the lead 1110 and the pulse generator 1105 is shownin FIG. 7C, described in more detail below.

The lead 1110, shown in more detail in FIG. 7B, extends from a proximalend 1112, where it is coupled with the pulse generator 1105, and extendsto a distal end 1114, which is coupled with a portion of a heart 1115,in the implanted condition (FIG. 7A). The proximal end 1112 of the lead1110 includes an overmolded portion 1124 which assists in sealing thelead 1110 to the pulse generator 1105. The distal end 1114 of the lead1110 includes at least one electrode 1116 which electrically couples thelead 1110 with the heart 1115. The electrode 1116 is either a unipolaror bipolar type electrode. In one embodiment, multiple electrodes areprovided. At least one electrical conductor (FIG. 9B) is disposed withinthe lead 1110 and electrically couples the electrode 1116 with theproximal end 1112 of the lead 1110. The electrical conductors carryelectrical current and pulses between the pulse generator 1105 and theelectrode 1116 located in the distal end 1114 of the lead 1110.

The body 1111 of the lead 1110, in one embodiment, is cylindrical inshape, and is made of a tubing material formed of a biocompatiblepolymer suitable for implementation within the human body. Although notrequired, the tubing is made from a silicone rubber type polymer. Thelead 1110 travels from the pulse generator 1105 and into a major veinand the distal end 1114 of the lead 1110, in one embodiment, is placedinside the heart 1115. The lead will be either actively or passivelyaffixed to the endocardial wall of a chamber of the heart, depending onthe embodiment.

FIGS. 8, 9A, and 9B illustrate another embodiment of the lead includinga press-fit design. The assembly 1200 includes a terminal pin 1210, asleeve 1230, and an outer terminal ring 1260, which are all coupledtogether such that, after assembly, axial movement of the individualcomponents is prevented, as further described below. The terminal pin1210 and the outer terminal ring 1260 each provide an electricalconnection in between the lead 1110 and the pulse generator 1105, asshown in FIG. 7C, and as further discussed below. The terminal pin 1210extends from a first end 1212 to a second end 1214. The second end 1214is adapted for coupling with the pulse generator 1105, as discussedabove (FIGS. 7A and 7C). The first end 1212 is adapted to be insertedinto other components of the assembly 1200, specifically the sleeve1230, as will be further described below. The first end 1212 of theterminal pin 1210 includes a tapered portion 1216 which facilitatesinsertion of the terminal pin 1210 into the sleeve 1230. In addition,the terminal pin 1210 includes an assembly portion 1220 which isdisposed near the first end 1212.

The assembly portion 1220, in one embodiment, includes an outer surface1222 which extends toward an annular ridge 1224. The outer surface 1222is adapted to be received within the sleeve 1230, as described below.The outer surface 1222 is tapered from the first end 1212 towards theannular ridge 1224. The annular ridge 1224 forms an engaging surfacewhich is received and retained by the sleeve, as further describedbelow.

The terminal pin 1210 also includes an internal surface 1218 whichdefines a lumen 1219 therein. The lumen 1219 extends through theterminal pin 1210 from the first end 1212 to the second end 1214 andallows for instruments, such as catheters, stylets, or guidewires, to beinserted through the terminal pin 1210 and through the lead 1110 (FIG.7B). In addition, the internal surface 1218 of the terminal pin 1210provides a coupling surface for a first conductor 1280, as illustratedin FIG. 9B, whereat the first conductor 1280 is electrically coupledwith the terminal pin 1210. The first conductor 1280 provides anelectrical connection between the terminal pin 1210 and an electrode ofthe lead 1110.

As mentioned above, the assembly 1200 also includes a sleeve 1230. Inone embodiment, the sleeve 1230 is an insulator between the terminal pin1210 and the outer terminal ring 1260, where the sleeve 1230electrically insulates the terminal pin 1210 from the outer terminalring 1260. In addition, the sleeve 1230 provides a mechanical connectionbetween the terminal pin 1210 and the outer terminal ring 1260. Thesleeve 1230 extends from a first end 1234 to a second end 1236, wherethe first end 1234 of the sleeve 1230 couples with the outer terminalring 1260. The second end 1236 is adapted to couple with the terminalpin 1210. Disposed through the sleeve 1230 is a bore 1232, where thebore 1232 is adapted to receive the terminal pin 1210 therein. The bore1232 allows for instruments, such as catheters, stylets, or guidewires,to be inserted through the sleeve 1230 and through the lead 1110 (FIG.11B).

The bore 1232 includes an internal surface 1238 which has a couplingfeature 1242 thereon. In one embodiment, the coupling feature 1242includes an annular shoulder 1244. The shoulder 1244 engages the annularridge 1224 of the terminal pin 1210. The sleeve 1230 also includes anexternal surface 1240. The external surface 1240, in one embodiment, isengaged by the outer terminal ring 1260, and is tapered. In oneembodiment, the taper extends from the second end 1236 toward the firstend 1234 of the sleeve 1230.

The assembly 1200 also includes an outer terminal ring 1260 whichextends from a first end 1262 to a second end 1264. The outer terminalring 1260 includes a coupling portion 1266 which is formed, in oneembodiment, on an internal surface 1268 of the outer terminal ring 1260.In one embodiment, the internal surface 1268 of the outer terminal ring1260 is sized to receive the external surface 1240 of the sleeve 1230therein, such that an interference fit or a press-fit is createdthereby. The interference fit between the sleeve 1230 and the outerterminal ring 1260 retains the sleeve 1230 axially to the outer terminalring 1260.

To assemble the assembly 1200, the first end 1212 of the terminal pin1210 is inserted into the second end 1236 of the sleeve 1230. Theterminal pin 1210 is inserted until the annular ridge 1224 engages withthe shoulder 1244 of the sleeve 1230. Once the terminal pin 1210 iscoupled with the sleeve 1230, the sleeve 1230 is then coupled with theouter terminal ring 1260 and axial movement between the sleeve 1230 andthe outer terminal ring 1260 is prevented. The first end 1234 of thesleeve 1230 is inserted into the second end 1264 of the outer terminalring 1260. The sleeve 1230 is inserted into the outer terminal ring 1260until the interference fit is created between the two. Alternatively, inanother embodiment, the sleeve 1230 can be assembled first with theouter terminal ring 1260 prior to insertion of the terminal pin 1210into the sleeve 1230.

The terminal pin 1210 and the outer terminal ring 1260 are both formedfrom conductive material. The sleeve 1230 is formed from a nonconductivematerial, and acts as an insulator between the terminal pin 1210 and theouter terminal ring 1260. The sleeve 1230 can be formed from varioushigh-performance engineering plastics, unreinforced and reinforcedmaterials including, but not limited to polysulfone, polyimide,polyamide, polyacetal, polyketone, polyester, polycarbonate, polyolefin,or liquid crystal polymers. Alternatively, the sleeve 1230 is formedfrom the materials discussed in the above embodiments. These materialsare appropriate for the sleeve 1230 described for FIGS. 8 and 9, andalso for all of the embodiments discussed above and below.

FIGS. 10 and 11 illustrate another embodiment of a snap-fit assembly1300, which generally includes a terminal pin 1310, a sleeve 1340, andan outer terminal ring 1360. The terminal pin 1310 is adapted to becoupled with the pulse generator 1105 as shown in FIG. 7C. The sleeve1340 is adapted to coupled with the terminal pin 1310 and the outerterminal ring 1360. The terminal pin 1310 extends from a first end 1312to a second end 1314, and includes a coupling portion 1320 integraltherewith. The coupling portion 1320 is formed on an external surface ofthe terminal pin 1310, and in one embodiment, comprises an annularflange 1322. The annular flange 1322, which can partially or completelyencircle the outer surface of the terminal pin 1310, includes matingsurfaces 1324 which are adapted to engage with the sleeve 1340, as willbe described below.

The sleeve 1340 extends from a first end 1342 to a second end 1344, andincludes a first set of coupling features 1345. The first set ofcoupling features 1345 are disposed proximate to the first end 1342 ofthe sleeve 1340. In one embodiment, the first set of coupling features1345 include a first set of cantilever hooks 1346. The first set ofcantilever hooks 1346 are adapted to deflect from a hinge point 1347 andare also adapted to couple with a portion of the outer terminal ring1360. The first set of cantilever hooks 1346 further include, in anotherembodiment, mating surfaces 1348. The mating surfaces 1348 are disposedproximate to tapered portions 1349 of the first set of cantilever hooks1346. It should be noted that the first set of cantilever hooks 1346refer to a plurality of coupling features, such as cantilever hooks,however, a single cantilever hook can also be used.

Disposed proximate to the second end 1344 of the sleeve 1340 are asecond set of coupling features 1356. In one embodiment, the second setof coupling features 1356 comprise a second set of cantilever hooks1350. The second set of cantilever hooks 1350 are adapted to couple withthe coupling portion 1320 of the terminal pin 1310. The second set ofcantilever hooks 1350, in another embodiment, each include a recess 1352formed therein. The recess 1352 of each of the second set of cantileverhooks 1350 is adapted to receive the annular flange 1322 therein. Itshould be noted that although a second set of cantilever hooks 1350 aredescribed herein, a single cantilever hook can also be used. A taperedingress 1358 is formed on the second set of cantilever hooks 1350 tofacilitate insertion of the terminal pin 1310 therethrough. In yetanother embodiment, the sleeve 1340 also includes a positive stop 1354.The positive stop 1354 has a surface which rests against a portion ofthe outer terminal ring 1360, preventing further movement thereof.

The outer terminal ring 1360, which couples with the sleeve 1340,extends from a first end 1362 to a second end 1364, and has anintermediate portion 1363 therebetween. The outer terminal ring 1360includes coupling features 1366, which in one embodiment are disposedproximate to the intermediate portion 1363. The coupling features 1366,in another embodiment, include cutouts 1368. The number of cutouts 1368corresponds to the number of hooks in the first set of cantilever hooks1346 of the sleeve 1340. The cutouts 1368 also correspond in shape toreceive the first set of cantilever hooks 1346 therein. In oneembodiment, the cutouts 1368 comprise circular apertures. In anotherembodiment, the coupling features 1366 each include a mating surface1370, which is disposed adjacent the mating surfaces 1348 of the sleeve1340 when the sleeve 1340 is assembled to the outer terminal ring 1360.

To assemble the snap-fit assembly 1300, the terminal pin 1310 is coupledwith the sleeve 1340, and the sleeve 1340 is coupled with the outerterminal ring 1360. The terminal pin 1310 can be assembled first intothe sleeve 1340, alternatively, the sleeve can first be coupled with theouter terminal ring 1360. To assemble the terminal pin 1310 to thesleeve 1340, the first end 1312 of the terminal pin 1310 is insertedinto the second end 1344 of the sleeve 1340. As the terminal pin 1310 isfurther inserted into the sleeve 1340, the second set of cantileverhooks 1350 are deflected by the annular flange 1322. The terminal pin1310 is further inserted into the sleeve 1340 until the annular flange1322 is seated within the recess 1352. The terminal pin 1310 and thesleeve 1340 assembly is then coupled with the outer terminal ring 1360.

The first end 1342 of the sleeve 1340 is inserted into the second end1364 of the outer terminal ring 1360. As the first end 1342 of thesleeve 1340 is inserted, the first set of cantilever hooks 1346 aredeflected. The sleeve 1340 is further inserted into the outer terminalring 1360 until the tapered portion 1349 of the first set of cantileverhooks 1346 are seated within the cutouts 1368 of the outer terminal ring1360. The mating surfaces 1348 of the cantilever hooks 1346 are placedadjacent to the mating surface 1370 of the outer terminal ring 1360.

The terminal pin 1310 and the outer terminal ring 1360 are each formedof a conductive material. The sleeve 1340 is formed from a nonconductivematerial, and acts as an insulator between the terminal pin 1310 and theouter terminal ring 1360, in one embodiment. The sleeve 1340 can beformed from various high-performance engineering plastics, unreinforcedand reinforced materials including, but not limited to polysulfone,polyimide, polyamide, polyacetal, polyketone, polyester, polycarbonate,polyolefin, or liquid crystal polymers.

FIGS. 12 and 13 illustrate another embodiment of a snap-fit assembly1400 which generally includes a terminal pin 1410, a sleeve 1440, and anouter terminal ring 1470. The sleeve 1440 is adapted for coupling withthe outer terminal ring 1470 and the terminal pin 1410. The terminal pin1410 extends from a first end 1412 to a second end 1414 and includes acoupling portion 1420. In one embodiment, the coupling portion 1420includes tapered projections 1422 which extend away from an externalsurface of the terminal pin 1410. Alternatively, the tapered projections1422 can have other shapes such as a rounded projection. The taperedprojections 1422 include at least one mating surface 1424, for couplingwith a portion of the sleeve 1440, as discussed further below. Althougha plurality of projections 1422 are discussed, a single projection canalso be used.

The sleeve 1440 extends from a first end 1442 to a second end 1444, andincludes a first set of coupling features 1445 for coupling with theouter terminal ring 1470. In addition, the sleeve 1440 includes a secondset of coupling features 1450 for coupling with the terminal pin 1410.

The second set of coupling features 1450, in one embodiment, comprisecutouts 1452 formed in cantilever panels 1453. The cantilever panels1453 are adapted to deflect when an internal or external force is placedthereon. The cutouts 1452 correspond in size and shape and are adaptedto receive therein the tapered projections 1422 of the terminal pin1410. In another embodiment, the number of cutouts 1452 correspond tothe number of tapered projections 1422. The cutouts 1452 include matingsurfaces 1454 which are adjacent to the mating surfaces 1424 of theterminal pin 1410 when the sleeve 1440 is assembled with the terminalpin 1410.

As mentioned above, the sleeve 1440 also includes a first set ofcoupling features 1445 for coupling the sleeve 1440 with the outerterminal ring 1470. The first set of coupling features 1445, which inone embodiment are disposed at the first end 1442 of the sleeve 1440,comprise cantilever hooks 1446 which include tapered portions 1447 andalso mating surfaces 1448. The cantilever hooks 1446 are adapted todeflect when an external or internal force is placed thereon. The firstset of coupling features 1445 are adapted to be received by the outerterminal ring 1470. In another embodiment, a positive stop 1456 isformed integral with the sleeve 1440 and is disposed adjacent to thefirst set of coupling features 1445.

The outer terminal ring extends from a first end 1474 to a second end1476 and includes an inner surface 1472 which receives the sleeve 1440therein. The outer terminal ring 1470 further includes snap-fit couplingfeatures 1478. In one embodiment, the snap-fit coupling features 1478comprise a tapered surface 1484 formed proximate to the second end 1476of the outer terminal ring 1470. The tapered surface 1484 is formed neara ridge 1480, which engages with the first set of coupling features 1445of the sleeve 1440. In another embodiment, the coupling features 1478include a mating surface 1482 which is placed adjacent to the matingsurfaces 1448 of the sleeve 1440.

To form the snap-fit assembly 1400, the terminal pin 1410 is assembledwith the sleeve 1440 and the sleeve 1440 is assembled with the outerterminal ring 1470. However, the sleeve 1440 can be assembled with theouter terminal ring 1470 prior to assembly of the terminal pin 1410 withthe sleeve 1440. To assemble the terminal pin 1410 with the sleeve 1440,the first end 1412 of the terminal pin 1410 is inserted into and throughthe second end 1444 of the sleeve 1440. The first end 1412 is inserteduntil the tapered projections 1422 are seated within the second set ofcoupling features 1450 of the sleeve 1440. As the terminal pin 1410 isinserted through the sleeve 1440, the tapered projections 1422 deflectthe cantilever panels 1453 outward of the sleeve 1440. The cantileverpanels 1453 are deflected until the tapered projections 1422 are seatedwithin the cutouts 1452 of the sleeve, and the mating surfaces 1454 ofthe cutouts 1452 abut the mating surfaces 1424 of the terminal pin 1410.

To assemble the sleeve 1440 to the outer terminal ring 1470, the firstend 1442 of the sleeve 1440 is inserted into the second end 1476 of theouter terminal ring 1470. As the sleeve 1440 is inserted into the outerterminal ring 1470, the first set of coupling features 1445 aredeflected as they approach the tapered surface 1484 of the outerterminal ring. The sleeve 144Q is further inserted until the matingsurfaces 1448 are seated against the mating surface 1482 of the outerterminal ring. The cantilever hooks 1446 are retained by the annularridge 1480 of the outer terminal ring 1470.

The terminal pin 1410 and the outer terminal ring 1470 are each formedof a conductive material. The sleeve 1440 is formed from a nonconductivematerial, and acts as an insulator between the terminal pin 1410 and theouter terminal ring 1470, in one embodiment. The sleeve 1440 can beformed from various high-performance engineering plastics, unreinforcedand reinforced materials including, but not limited to polysulfone,polyimide, polyamide, polyacetal, polyketone, polyester, polycarbonate,polyolefin, or liquid crystal polymers.

FIGS. 14 and 15 illustrate another embodiment of a snap-fit assembly1500, which includes generally a terminal pin 1510, a sleeve 1540, andan outer terminal ring 1570. The terminal pin 1510 extends from a firstend 1512 to a second end 1514, and includes at least one couplingportion 1516. In one embodiment, the coupling portion 1516 is disposedbetween the first end 1512 and the second end 1514 of the terminal pin1510. In another embodiment, the coupling portion 1516 comprises anannular projection 1518 which extends from an external surface of theterminal pin 1510. The annular projection 1518, in another embodiment,includes a tapered surface 1522 and also a mating surface 1520. Thecoupling portion 1516 allows for the terminal pin 1510 to be coupledwith the sleeve 1540 using a snap-fit connection.

The sleeve 1540 is adapted to couple with both the terminal pin 1510 andalso the outer terminal ring 1570, and extends generally from a firstend 1542 to a second end 1544. Proximate to the first end 1542, is afirst coupling feature 1546, which allows for the sleeve 1540 to becoupled with the outer terminal ring 1570. In one embodiment, the firstcoupling feature 1546 comprises an annular projection 1548 including atapered surface 1550 and a mating surface 1552. The sleeve 1540 alsoincludes a second coupling feature 1554 which, in one embodiment,comprises an annular recess 1556. In yet another embodiment, the annularrecess 1556 includes a ridge 1558 and also a mating surface 1560, whichis adapted to couple with the annular projection 1518.

The outer terminal ring 1570 is adapted to couple with the sleeve 1540,and generally extends from a first end 1572 to a second end 1574. Theouter terminal ring 1570 is defined in part by an inner surface 1576which is adapted to receive a portion of the sleeve 1540 therein. Theouter terminal ring 1570 further includes at least one snap-fit couplingfeature 1578 which allows for the sleeve 1540 to be coupled with theouter terminal ring 1570. In one embodiment, the coupling feature 1578includes a tapered ingress 1582 which extends to a ridge 1580. The ridge1580 includes a mating surface 1584, and is adapted to retain the firstcoupling feature 1546 of the sleeve 1540. In one embodiment, the taperedingress 1582 and/or the ridge 1580 are formed on the inner surface 1576of the outer terminal ring 1570. In another embodiment, the taperedingress 1582 is formed annularly of the inner surface 1576.

To assemble the snap-fit assembly 1500, the terminal pin 1510 is coupledwith the sleeve 1540, and the sleeve 1540 is coupled with the outerterminal ring 1570. It should be noted however, that the sleeve 1540 canalso be first coupled with the outer terminal ring 1570 and then theterminal pin 1510 is coupled with the sleeve 1540. To couple theterminal pin 1510 to the sleeve 1540, the first end 1512 of the terminalpin 1510 is inserted into the second end 1544 of the sleeve 1540. Theterminal pin 1510 is inserted until the coupling portion 1516 is seatedwithin the second coupling feature 1554, of the sleeve. Once the annularprojection 1518 is seated within the annular recess 1556, the matingsurface 1520 abuts the mating surface 1560 of the sleeve 1540.

To assemble the sleeve 1540 to the outer terminal ring 1570, the firstend 1542 of the sleeve 1540 is inserted into the second end 1574 of theouter terminal ring 1570. As the sleeve 1540 is inserted into the outerterminal ring 1570, the tapered surface 1550 deflects the taperedingress 1582 of the outer terminal ring 1570. The sleeve 1540 is furtherinserted into the outer terminal ring 1570, until the mating surface1552 of the first coupling feature 1546 abuts the mating surface 1584 ofthe outer terminal ring 1570.

The terminal pin 1510 and the outer terminal ring 1570 are each formedof a conductive material. The sleeve 1540 is formed from a nonconductivematerial, and acts as an insulator between the terminal pin 1510 and theouter terminal ring 1570, in one embodiment. The materials suitable forthe sleeve 1540 are similar to those described for the sleeve discussedabove in earlier embodiments The snap-fit assembly 1500 provides severaladvantages in that the assembly allows for rotational movement, yetprevents axial movement of the terminal pin 1510 relative to the sleeve1540, and the sleeve 1540 relative to the outer terminal ring 1570. Therotational movement which is allowed by the snap-fit assembly 1500 isadvantageous since the snap-fit assembly 1500 can be used in combinationwith retractable lead designs, or leads which otherwise requirerotational movement and yet simultaneously prevent axial movement.

FIGS. 16, 17, and 18 illustrate another embodiment of a snap fitassembly 1600, which includes generally a terminal pin 1620 and an outerterminal ring 1660. The terminal pin 1620 and the outer terminal ring1660 are adapted to couple together at a snap-fit coupling, as furtherdescribed below.

The terminal pin 1620 extends from a first end 1622 to a second end1624, and includes a snap-fit coupling portion 1626. In one embodiment,the coupling portion 1626 is disposed between the first end 1622 and thesecond end 1624. It should be noted that the coupling portion 1626 canbe disposed on an external surface or an internal surface of theterminal pin 1620. In another embodiment, the coupling portion 1626comprises an annular projection 1640, as shown in FIG. 17. The annularprojection 1640 has a semi-circular cross-section, as shown in FIG. 16.In another embodiment, the coupling portion 1626 comprises at least oneprojection 1642, which does not extend completely around the outersurface of the terminal pin 1620, as illustrated in FIG. 17. A pluralityof projections 1643 can also be provided, as shown in FIG. 18. Inanother embodiment, the plurality of projections 1643 are spaced 90degrees apart from one another.

Disposed through the terminal pin 1620 a bore 1630, where the bore 1630extends from the first end 1622 to the second end 1624 of the terminalpin 1620. The bore 1630 allows for instruments, such as catheters,stylets, or guidewires, to be inserted through the terminal pin 1620 andthrough the lead 1110 (FIG. 7B).

In yet another embodiment, an insulator is disposed between the terminalpin 1620 and the outer terminal ring 1660. The insulator can be a shim,a tube, a wedge, or a coating placed between the terminal pin 1620 andthe outer terminal ring 1660. In one embodiment, a dielectric coating1628 is disposed on the interfacing surfaces between the terminal pin1620 and the outer terminal ring 1660. In another embodiment, thecoating is disposed over the coupling portion 1626. The dielectriccoating 1628 provides insulation for the coupling portion 1626 and/orthe surface of the terminal pin 1620. Various insulating materials areappropriate for use as the coating 1628 such as: tungsten carbide,aluminum oxide, chromium oxide, zirconium oxide, magnesium zirconate,acrylic, epoxy, parylene, polyurethane, silicone, teflon, or molybdenumdisulfide. Other materials which are also dielectric, biocompatible,wear resistant, and has a low coefficient of friction would also beappropriate. The coupling portion 1626 of the terminal pin 1620 isadapted to snap-fit with a coupling portion of the outer terminal ring1660.

The outer terminal ring 1660 extends from a first end 1662 to a secondend 1664, and includes a snap-fit coupling portion 1668. The snap-fitcoupling portion 1668, in one embodiment, is disposed on an intermediateportion 1665 of the outer terminal ring 1660. In another embodiment, thecoupling portion 1668 is disposed on an inner surface 1666 of the outerterminal ring 1660. The coupling portion 1668 comprises an annularrecess 1670 which is sized and positioned to receive the snap-fitcoupling portion 1626 of the terminal pin 1620 therein.

To assemble the snap-fit assembly 1600, the terminal pin 1620 is coupledwith the outer terminal ring 1660. To assembly the terminal pin 1620 tothe outer terminal ring 1660, the first end 1622 of the terminal pin1620 is inserted into the second end 1664 of the outer terminal ring1660. The terminal pin 1620 is inserted until the annular projection1640 is seated within the annular recess 1670 of the outer terminal ring1660. Once the projection 1640 is seated within the recess 1670, furtheraxial movement is prevented. However, rotational movement of theterminal pin 1620 relative to the outer terminal ring 1660 is permitted.

Several embodiments are described above which relate to snap fitfeatures for the terminal pin and the outer terminal ring and,optionally, the sleeve. It should be noted that the features shown inthe drawings can be exchanged between embodiments shown in the variousdrawings. In addition, the coupling features have been described on anexternal surface of one component which mates with an internal surfaceof another component. However, the coupling features can be moved frominternal to external surfaces and vice versa to accommodate the snap-fitfeatures and/or the press-fit features. Furthermore, the lead design isnot limited to the particular embodiments shown or described above, andcan be applied to various medical devices. It should be further notedthat embodiments discussed for the distal end of the lead can becombined with any of the embodiments for the proximal end of the lead.

The lead assembly described above provides several advantages, forexample, the ease of manufacturability is increased in that through-puttimes are reduced. The individual components can be snapped together, asopposed to waiting for messy bonding or long cure times. Bonding blocks,used for the bonding process, would be eliminated, which are expensiveand difficult and costly to clean. A consistent and increased strengthof coupling would be achieved using the snap fit design since bonding isvariable based on the operator. Yet another advantage is that thegeometry of the snap fit connector provides an insulation with a knownthickness, which allows for a repeatable dielectric strength.Furthermore, the active fixation element of the lead does not requirethe use of a stylet, since the terminal pin is used to extend andretract the active fixation element. In addition, the movement assemblyallows for the lead to withstand high shearing forces applied betweenthe terminal pin and the outer terminal components such as the ring.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reviewing the abovedescription. The scope of the invention should, therefore, be determinedwith reference to the appended claims, along with the full scope ofequivalents to which such claims are entitled.

1. A lead for a medical device, the lead comprising: a lead bodyextending from a distal end portion to a proximal end portion; at leastone conductor disposed within the lead body and extending from theproximal end portion; an electrically conductive terminal pin disposedat the proximal end portion of the lead body, the electricallyconductive terminal pin having at least one tapered annular flange; andan insulative sleeve coupled with the electrically conductive terminalpin with a snap-fit connection.
 2. The lead as recited in claim 1,wherein the snap-fit connection comprises a rotatable snap-fittedconnection that allows rotation of the terminal pin relative to thesleeve after the sleeve is snap-fittedly coupled with the terminal pin.3. The lead as recited in claim 1, further comprising a fixation helixmechanically and electrically coupled with the terminal pin and the atleast one conductor such that as the terminal pin is rotated, thefixation helix is rotated.
 4. The lead as recited in claim 1, whereinthe snap-fit connection comprises the annular flange received in anannular recess.
 5. The lead as recited in claim 1, further comprising anouter terminal ring coupled with the insulative sleeve.
 6. The lead asrecited in claim 5, wherein the sleeve further comprises a positive stopfor the outer terminal ring.
 7. The lead as recited in claim 5, whereinthe sleeve comprises a snap-fit coupling disposed proximate to the outerterminal ring.
 8. The lead as recited in claim 1, wherein at least thesleeve is coated with a non-conductive material.
 9. The lead as recitedin claim 8, wherein the non-conductive coating is disposed on the outersurface of the terminal pin.
 10. The lead as recited in claim 9, whereinnon-conductive material is disposed between the outer terminal ring andthe terminal pin.
 11. The lead as recited in claim 1, wherein the sleeveforms an insulator between the outer terminal ring and the terminal pin.12. The lead as recited in claim 1, wherein the sleeve is formed ofpolyetheretherketone.
 13. A lead comprising: a lead body extending froma distal end portion to a proximal end portion; a conductor disposedwithin the lead body and extending from the proximal end portion; anouter terminal ring coupled with the lead body; a terminal pin disposedat the proximal end of the lead body; and a sleeve is coupled with theouter terminal ring or the terminal pin, the sleeve includes aprojection mated with a recess within the terminal pin, and theprojection comprises an annular projection disposed about acircumference of the sleeve, and the recess comprises an annular recessdisposed about a circumference of the terminal pin.
 14. The lead asrecited in claim 13, further comprising a male component on the sleeveand a female component on the terminal pin.
 15. The lead as recited inclaim 14, further comprising a male component on the terminal pin and afemale component on the sleeve.
 16. The lead as recited in claim 14,wherein the male component comprises an annular projection and thefemale component comprises an annular recess.
 17. The lead as recited inclaim 13, further comprising an active fixation mechanism disposedproximate to the distal end of the lead body, the active fixationmechanism including a movement assembly coupled therewith; the movementassembly configured to extend and retract the active fixation mechanism,the movement assembly including: an internally threaded portion; and anexternally threaded collar engaged with the internally threaded portion.18. A lead comprising: a lead body extending from a distal end to aproximal end; a conductor disposed within the lead body and extendingfrom the distal end to the proximal end of the lead body; a terminal pindisposed at the proximal end of the lead body; an insulative sleeve iscoupled with the terminal pin, the sleeve includes a projection matedwith a recess within the terminal pin, and the projection comprises anannular projection disposed about a circumference of the sleeve; and anactive fixation mechanism disposed proximate to the distal end of thelead body, the active fixation mechanism including a movement assemblycoupled therewith; the movement assembly configured to extend andretract the active fixation mechanism, the movement assembly including:a housing having an internally threaded portion; and an externallythreaded collar engaged with the internally threaded portion.
 19. Thelead as recited in claim 18, wherein the movement assembly furthercomprises an internally threaded insert disposed within the lead body,where the threaded collar is engaged with the threaded insert.
 20. Thelead as recited in claim 18, wherein the externally threaded collarcomprises an electrode base.
 21. The lead as recited in claim 1S,further comprising a fixation helix coupled with an externally threadedelectrode base, and an outer threaded shell having internal threads, theouter threaded shell disposed within the distal end of the lead body,the outer threaded shell threadingly coupled with the electrode base.22. The lead as recited in claim 21, wherein the conductor ismechanically and electrically coupled with the terminal pin and thefixation helix such that as the terminal pin is rotated, the fixationhelix is rotated.